This invention relates to an ink composition, and particularly to an erasable ink composition.
Various pencil lead compositions and erasable ink compositions have existed in the prior art. Examples of these compositions are disclosed in U.S. Pat. Nos. 2,852,397, 4,687,791, 2,715,388, 4,209,332, 2,239,142, and 4,371,632.
U.S. Pat. No. 2,852,397 disclosed an erasable ink composition which consists essentially of a stable colloidal dispersion of graphite particles in a light petroleum oil, and a tar-like carrier consisting of petroleum tar, bituminous distillate residue and asphalt dissolved in a petroleum thinner and oil. A metallic soap selected from a group consisting of oleic acid and stearic acid may be added to the above composition so as to keep the writing implement which employs the ink composition in a clean condition.
U.S. Pat. No. 4,687,791 discloses an erasable ball-point pen ink which is comprised of a rubber component, a volatile solvent, a pigment such as graphite, a non-volatile solvent, fine powders of silicon dioxides.
U.S. Pat. No. 2,239,142 discloses a pencil lead composition which consists of a fired mix of graphite and clay, impregnated with an ionized sodium chloride solution. This patent also describes the use of ethyl alcohol as a non-volatile vehicle to impregnate the pencil lead.